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<p>The initial stress state (e.g., maximum principal stress <i>σ</i><sub>1</sub>) plays a crucial role in governing the crack evolution and stability of the prefractured rock, and elevated temperatures arising from sources such as nuclear waste decay, coal fires, or tunnel fires exert additional influence on the shear behavior of prefractured rock, posing major challenges to the stability and safety of deep underground rock engineering projects. In this study, prefractured granite specimens were firstly subjected to various initial <i>σ</i><sub>1</sub> (80 MPa, 188 MPa, 282 MPa and 320 MPa) under a true triaxial stress state (<i>σ</i><sub>2</sub> = 80 MPa and <i>σ</i><sub>3</sub> = 20 MPa). The rock was then heated to different target temperatures, after which <i>σ</i><sub>1</sub> was continuously applied until shear failure occurred under thermal–mechanical coupling conditions. Results indicate that peak strength, shear stress drop, dynamic slip and shear damage first increase and then decrease with increasing initial <i>σ</i><sub>1</sub> at the same temperature of 200&#xa0;°C. This behavior reflects a transition from limited asperity damage and effective thermally induced fracture closure under low initial <i>σ</i><sub>1</sub> to intensified asperity damage, higher slip tendency, and inhibited thermal closure under higher <i>σ</i><sub>1</sub>. Increasing temperature (from 25 ℃ to 300 ℃) generally increases the strength and shear damage under a constant initial <i>σ</i><sub>1</sub> (188 MPa or 320 MPa), and the strength, shear stress drop, and dynamic slip are higher for specimens under 188 MPa at all test temperatures. Temperature elevation promotes fracture closure and enhances shear frictional resistance, resulting in a pronounced thermal strengthening effect. However, under a higher initial <i>σ</i><sub>1</sub> (i.e., 320 MPa), severe initial asperity damage reduces the energy accumulation capacity and frictional resistance, and thermal closure is inhibited, resulting in a smaller strengthening effect compared with that under 188&#xa0;MPa. This research will provide important experimental evidence for modeling the thermal–mechanical shear behavior of prefractured rock in deep underground rock engineering.</p>

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Influence of Initial Maximum Principal Stress on Thermal–Mechanical Shear Behavior of Fractured Granite

  • 期刊论文

  • 发表日期：

    2026年7月24日

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  • Zhufeng Yue,
  • Fanzhen Meng,
  • Hui Zhou,
  • Dongliang Tian,
  • Yuantao Wen,
  • Yashi Yang,
  • Jie Liu,
  • Wu Cai

摘要

The initial stress state (e.g., maximum principal stress σ1) plays a crucial role in governing the crack evolution and stability of the prefractured rock, and elevated temperatures arising from sources such as nuclear waste decay, coal fires, or tunnel fires exert additional influence on the shear behavior of prefractured rock, posing major challenges to the stability and safety of deep underground rock engineering projects. In this study, prefractured granite specimens were firstly subjected to various initial σ1 (80 MPa, 188 MPa, 282 MPa and 320 MPa) under a true triaxial stress state (σ2 = 80 MPa and σ3 = 20 MPa). The rock was then heated to different target temperatures, after which σ1 was continuously applied until shear failure occurred under thermal–mechanical coupling conditions. Results indicate that peak strength, shear stress drop, dynamic slip and shear damage first increase and then decrease with increasing initial σ1 at the same temperature of 200 °C. This behavior reflects a transition from limited asperity damage and effective thermally induced fracture closure under low initial σ1 to intensified asperity damage, higher slip tendency, and inhibited thermal closure under higher σ1. Increasing temperature (from 25 ℃ to 300 ℃) generally increases the strength and shear damage under a constant initial σ1 (188 MPa or 320 MPa), and the strength, shear stress drop, and dynamic slip are higher for specimens under 188 MPa at all test temperatures. Temperature elevation promotes fracture closure and enhances shear frictional resistance, resulting in a pronounced thermal strengthening effect. However, under a higher initial σ1 (i.e., 320 MPa), severe initial asperity damage reduces the energy accumulation capacity and frictional resistance, and thermal closure is inhibited, resulting in a smaller strengthening effect compared with that under 188 MPa. This research will provide important experimental evidence for modeling the thermal–mechanical shear behavior of prefractured rock in deep underground rock engineering.